This invention relates to a metallothermic process for the reduction of rare earth metals, more particularly, this invention relates to the reductants used for reducing neodymium chloride to neodymium metal.
Rare earth metals are normally formed by reducing rare earth oxides with granular calcium metal at high temperatures, for example 1100 degrees and up.
U.S. Pat. No. 4,578,242 discloses reducing neodymium oxide with granular calcium metal to form neodymium alloys with iron or zinc. The above process is carried out by reacting neodymium oxide with sodium or granular calcium in a molten calcium chloride-sodium chloride matrix and forming a neodymium-iron or neodymium-zinc alloy. This is done at 700 degrees C. in a helium atmosphere, after which the product alloy is allowed to phase separate, and is recovered. The byproduct calcium oxide accumulates in the reaction vessel and causes the melting point of the matrix to increase, limiting the number of cycles possible before an entirely new charge of salt is needed.
The disadvantage of using pure granules of calcium is that such material is difficult to handle and may pose a hazard for operators handling such material because of the temperatures involved with the process.
It is therefore desired to provide a process which is relatively cheaper, easier, and safer to prepare neodymium metal or neodymium/iron alloy via the calciothermic reduction of neodymium salts. It is further desired to provide a process which solves the problem of handling pure calcium metal, and allows the reaction to be run at lower temperatures.